Synthetic wool



Patented Oct. 8, 1940 SYNTHETIC WOOL Vernal B. Hardy, Wilmington, Del., asslgnor to E. I. du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware No Drawing. Application September 29, 1938, Serial No. 232,470

11 Claims.

This invention relates to artificial fibers and fabrics, and more particularly to the manufacture of synthetic wool.

An object of this invention is to prepare artificial wool-like filaments, fibers, yarns, fabrics and the like; A further object is to prepare a wool-like product having good strength, retentivity ofcrimp both wet and dry, heat stability and heat insulating properties. A still furtherv l0 object is to convert synthetic polymeric staple fibers into crimped or wool-like fibers. Other objects will appear hereinafter.

These objects are accomplished by spinning a drawing, that is upon application of stress in the solid state, yield oriented fibers. The cold drawn fibers show definite orientation along the fiber axis, whereas the undrawn filaments are substantially unoriented. The term "filament as used herein'refers to both oriented and unoriented filaments or threads which are drawn from the polymers regardless of whether the filaments or threads are long (continuous) or short (staple), while the term fiber refers more specifically to .the oriented filaments which are useful in the manufacture of yarn and fabrics as are natural textile fibers. Of this new class of fiber-forming materials, the polyamides form a particularly valuable subclass. Polyamides are of two types, those obtainable by polymerization of monoaminomonocarboxylic acids or their amide-forming derivatives, including caprolactam, and those obtainable by condensation polymerization from suitable diamine-dibasic acid mixtures or their equivalents. In these polyamides the amide groups form an integral part of the main chain of atoms in the polymer.

Veryattractive and durable fabrics can be prepared from the polyamide fibers mentioned pact and have the general appearance and feel of silk. While thesev fabrics find many uses, there is a demand for fabrics having the properties of wool, i. e., a crimped fiber structure. good heat insulating properties, and a loose, fluffy appear- 6 ance. Although numerous types of artificial fibers have been prepared which can be used to advantage 'as substitutes for cotton and silk, at-' tempts to prepare a fully satisfactory substitute for wool from materials other than the synthetic l0 fibers used in this invention have thus far been unsuccessful. Methods for preparing wool-like materials from polyamide filaments are described in application Serial Number 183,922, filed jointly by me and J. B. Miles January 7, 1938. Material may be obtained in accordance with the disclosure of the mentioned application which has an excellent crimp andwoolly nature but the methods are long, involved, and relatively expensive. Also the more desirable methods from an operating standpoint yield material of inferior crimp and wooliness.

I have now found that an excellent wool substitute can be prepared from polyamides of both the amino-acid and diamine-dibasic acidtypes bycarding staple fibers prepared from them, packing the carded web tightly into bales, and subjecting the bales to any one of a number of setting treatments, more fully described below.

When the material so treated is unpacked and W carded again, a web composed of excellently crimped, extremely wool-like filaments is obtained. The crimp, if produced under proper conditions, is stable to tension, friction, and water or steam at 100 C. or even higher temperatures.

A property of the synthetic polymeric filaments which I have found to be particularly. valuable in my process for obtaining wool-like products from the polyamide filaments is the: ability of these filaments to be permanently set in any de- I sired shape or position by means of heat treatments of various kinds. The setting conditions may vary widely. For example, if polyamide filaments are used the crimp can be introduced by treating them with steam from atmospheric pressure up to 120 lbs/sq. in. (100 C.-172 0.). Or it can be produced by treating the compressed filaments with water at temperatures above C., or with dry heat between C. and 150 C.,

or with various other agents having but a slight solvent action such as ethanol vapors between atmospheric pressure and 100 lbs/sq; in. (78 C.- 135 C.)., methanol vapor between atmospheric pressure and lbs/sq. in, pressure (66430 C.)

or, in general, with any mild swelling agent for 55 the filaments, preferably an hydroxylecontaining compound, at elevated temperatures. The conditions used will, of course, be dependent upon the nature of the textile filaments being crimped. e. g., their softening point or melting point, their stability to heat and to vapors at high temperatures, their susceptibility to being set in any desired position, their filament size, etc.

The time for which the treatment is applied to the compressed filaments is not unduly critical. Times of one minute or more to about ten minutes are to be preferred, although crimp of fair quality. may be obtained in even shorter times. Increasing the time of treatment or the temperature, or both, inordinately will of course tend to produce tendering.

Wool-like synthetic polymer fibers can be prepared from fibers of almost any diameter by this process. Fibers having deniers in the neighborhood of 2-20 are most useful. The crimp in the fibers is very irregular and wool-like in appearance- Some of the crimps are large, some small,

some in one plane, others in planes at angles' to these, and in some cases the entire filament is doubled back upon itself. The number of crimps per inch depends to some extent upon the fineness of the filaments, the amount of carding to which they are subjected, the tightness to which they were packed, the size of the bale into which they were packed, and the nature of the setting treatment. In generalyit may be said that the number of crimps per inch, the sharpness of the crimps, and their permanence can be made equal to or better than that of natural wool.

The following examples are illustrative of the methods for'practicing the invention:

Example I A sample of GOO-denier, 30-filament dull polyhexamethylene adipamide yarn was drawn 313% and cut into 4.7-inch staple. The staple was of 5.7 denier per filament and had a tenacity of 19.1 grams per filament. This staple was carded and the carded web was compressed into a small bale which was treated with steam at 25 lbs./sq.-in. pressure for 5 minutes. When the staple was dried and carded again it was found to have an excellent, wool-like crimp which was permanent to tension and to immersion in boiling water. The tenacity of the material so prepared was 18.2 grams per filament.

Example II Example III When a sample of carded polyhexamethylenl adipamide like that described in Example I was compressed into a small bale and treated with steam at 100 lbs./sq..in. pressure for one minute,

it was found to have an excellent, wool-like crimp crimp was permanent to boiling water. tension, mechanical friction, etc.

Example I V When a sample of dull, carded polyhexamethylene adipamide staple like that described in Examples I and III above was compressed into a small bale and treated with methanol vapors at 60 lbs/sq. in. for ten minutes, it was found to have an excellent, wool-like crimp when it was dried and carded again.

Example V A sample of 300-denier, 20-filament bright polyhexamethylene adipamide yarn was drawn 313% and cut into 4-inch staple of approximately 3.8 denier per filament. This material was carded and compressed into a small bale. It was then treated with ethanol vapors at 30 lbs/sq. in. pressure for minutes. When the material was dried and carded again it was found to have an excellent, wool-like crimp.

Example VI A sample of 440-denier, 30-filament bright polydecamethylene adipamide yarn was drawn 250% and cut into 6-inch staple of approximately 4.3 denier per filament. The staple was carded and compressed into a small bomb. Acetone vapors at 90 lb./sq. in. (approximately 121 C.) were introduced and maintained for 10 minutes. When the material was removed and carded it was found to have a good, woolly crimp.

The examples illustrate the preparation of crimped or wool-like fibers from bright, dull, fully drawn, andpartially drawn polyamide staple of various deniers per filament and diiferent staple lengths. Filaments of widely varying staple lengths are suitable for the process, although lengths of /2 inch to 10 inches are preferable. It is also possible to carry out the process of this invention using polyamide fibers modified by the incorporation of plasticizers, resins, oils, cellulose derivatives, dyes, pigments, etc.

A valuable class of polyamides for the preparation of wool-like fibers are those derived from diamines of formula NHrCHzRCHzNI-Is and dicarboxylic acids of formula HOOCCI-IzR'CHaCOOH and/or their amide-forming derivatives, in which R. and R" are divalent hydrocarbon radicals free from olefinic and acetylenic unsaturation and in which R has a chain length of at least 2 carbon atoms. An especially valuable group of polyamides within this class are those in which R is (CI-12).! and R is (CHaW, wherein a: and v are integers and a: is at least 2. As examples of polyamides which fall within one or both of these groups may be mentioned polytetramethylene adipamide, polytetramethylene suberamide, polytetramethylene sebacamide, polypentamethylene segacamide, polyhexamethylene adipamide, polyhexamethylene sebacamide. polyoctamethylene adipamide, polydecamethylene adipamide, polydecamethylene p-phenylene diacetamide, and poly-p-xylylene sebacamide.

When the polyamides are of the amino acid type and obtained by polymerizing monoaminomonocarboxylic acids, or their lactams or other amide-forming derivatives, a large number of polyamide-forming materials are also available. As additional examples of this type of polyamide,

there may be mentioned the polymers derived from '1-aminoheptoic acid, 9-aminononanoic acid,

, polymers of polyamides with these other polymeric materials. In fact, any filament in which a crimp can be set by a heat treatment is suitable for the process; for example, cellulose acetate filaments and viscose rayon filaments.

The two types of polyamides described herein may be obtained from various bifunctionalreactants which may be referred to a.s\polyamideforming compositions from which polyamides of the amino acid type can be obtained and may. consist of various materials in which molecules of 'the same substance combine through complementary amide-forming groups oneach molecule. The fiber-forming composition yielding polyamides of the diamine-dibasic acid type includes a diamine and any one of several materials, the molecules of which carry or yield under the conditions of the reaction, two amide-form-' ing. groups complementary to the two' amino groups of the amine. The reacting material of polyamide-forming compositions of the amino acid type includes monoamino monocarboxylic acids or amide-forming derivatives thereof (1. e., an ester, acid halide, anhydride,-amide or 19.0- tam); and monoamino mononitriles in the presence of water. The reacting material of polyamide-forming compositions of the diamine-dibasic acid type comprises a diamine and a complementary amide-forming reactant such as a dibasic acid or its amide-forming derivative. a dinitrlle in the presence of water, a diisocyanate, a diisothiocyanate, a diurethane, adithiodiurethane, or a tetrathiodiurethane. I

The setting treatment given the carded.and compressed staple may be of several types. In the'Examples I-V given above the staple was treated with vapors under pressure of swelling,

agents for the filaments. When steam is used, this pressure may vary all the way from atmospheric pressure to as high as; lbs./sq. in. When ethanol or methanol is usedthe pressures may similarly vary from atmospheric to 100 lbs/sq. in. or evenhigher. In like manner the crimp may be produced by treatingthe carded and compressed filaments with liquid water, ethanol, methanol, etc., at temperatures from 100? C. to C. or higher. Other liquids or vapors which may be used to produce the crimp include isobutanol, propanol, acetone, methyl ethyl ketone, dibutyl ether, amyl alcohol, toluene, etc.

While crimping with steamunder pressure is the preferred method, it is within the scope of this invention to produce the crimp in the compressed filaments by other methods; for example, by treating with dry heat at 100-200 C., with hot aqueous solutions of phenohformic acid, ethylene glycol, acetamide, hydrogen chloride, sodium chloride, or the like. In fact, hot aqueous solutions of a large variety of materials, which do not degrade or dissolve the fibers may be used. The best time over which to apply any of the crimping treatments is dependent upon a number of the above materials.

Although the process as described in the above .ha ve good dyeing characteristics.

examples is a batch process, it can also be carried out continuously using the principle of the'hay baler in which the carded fibers are led continusetting chamber and pushed out continuously on the other sideoi' the setting chamber as crimped staple fibers either in a form to 'be fed.

,This invention provides a convenient and card or in a wired economical method for the preparation of artificial wool-like fibers. In comparison with previously proposed methods of crimping polyamide filaments the process is simple and economical especially because it can be applied to fibers in bulk and involves the use of staple filaments which are cheaply obtained. It requires no unusual or intricate equipment, the equipment used being that found in standard textile practice.

Large batches of staplecan be treated in comparatively small space or a continuous process can be used to effect large output, again in a small fioor space.

The wool fibers obtained by the method described herein have excellent elastic properties, show fiber orientation when examined by X-rays,

are quite insensitive to moisture, have good resistance to. solvents andchemical reagents,-show little tendency to lose strength on aging. and Moreover, the fibers and fabrics prepared from the materials described by this invention have good heat insulating properties. Their tenacitles usually range between 2.5 and 4 g./d., depending upon the conditions under which the material was prepared.

The crimp obtained in the wool-like fibers re sulting from the present process is equal to that in natural wool and is permanent to boiling water. These artificial wool-like fibers are also equal to natural wool in crimp retention, heat insulating properties, dyeing characteristics, and are superior to wool in strength, heat stability, uniformity of characteristics, freedom from shrinkage, and low moisture regain. Unlike wool, they are not attacked by moths. The artificial wool-like products of this invention are quite stable at 150 C., whereas natural wool decomposes quite rapidly at this temperature with liberation of ammonia, hydrogen sulfide, and carbon disulfide. The process by which the artificial fibers of this invention are made is of such a character that modifying agents, for example delusterants and plasticizers, can be readily incorporated therewith. The fibers of this invention can be easily formed into yarns of the worsted type. These yarns can be knitted or woven into fabrics, rugs, and the like. If desired, other types of fibers and yarns, for example viscose rayon, acetate rayon,- cotton, silk, and wool, can be used in conjunction with the crimped fibers prepared by this invention in the preparation of fabrics. Ordinary, i. e., straight polyamide fibers and yarns, can also be used with the crimped material prepared by this invention. In contrast to other known synthetic wools, the product of this invention retains its crimp when wet. A bundle .of crimped polyamide fibers when wet and squeezed will spring back instead of remaining packed as will crimped cotton, viscose rayon, cellulose acetate rayon, or any other ously-into a] compressing device enclosed in the known wool substitute. This is also. true of the corresponding fabrics.

As many apparently widely different embodiments of this invention may be made-without departing from the spirit and scope thereof, it is to be understood that I do not limit myself to the specific embodiments thereof except as defined in the appended claims.

I claim: 1

1. In a process for making artificial wool, the steps comprising compressing a mass of staple synethtic linear polymer filaments, and setting the shape of the filaments resulting from said compressing of the filament mass by heating the filaments, while compressedin said mass. in the presence of a mild swelling agent.

2. In a process for making artificial wool, the steps comprising carding staple synthetic linear polymer filaments, compressing a mass of the carded staple filaments, and setting the shape of the filaments by heating the filaments, while compressed in said mass, in the presence of a mild swelling agent.

3. In a process for making artificialwool, the steps comprising cutting cold drawn synthetic linear polyamide filaments into staple fiber, carding the staple fiber, compressing the carded fiber into a bale, and setting the shape of the fibers by heating the fibers, while compressed in said bale, in the presence of a mild swelling agent.

. 4; In a process for making artificial wool, th steps comprising carding staple synthetic linear polyamide fibers, compressing the carded staple fibers into a bale, and setting the shape of the 7. The process set forth in claim 2 in which said polymer is a polyamide.

8. The process set forth in claim 2 in which said polymer is a polyamide obtainable from a diamine and a dibasic carboxylic acid. T 9. The process set forth in claim 2 in which said polymer is a polyamide obtainable from a monoaminomonocarboxylic acid.

10. The process set forth in claim 3 in which said polyamide is polyhexamethylene adlpamide.

11. The process set forth in claim 5 in which said polyamide is polyhexamethylene adipamide.

VERNAL R. HARDY. 

